Search

Carbon-based perovskite solar cells aroused huge attention for their simple, low-cost device fabrication processing and excellent stability. However, the fully low-temperature preparation and flexibility of carbon-based perovskite solar cells remain huge challenges. Here we demonstrate the fabrication of carbon-based perovskite solar cells processed at fully low-temperature, which take thermally evaporated cadmium sulfide as efficient electron transport layer, and obtain an optimal power conversion efficiency of 13.22%. With the decoration of PCBM, the separation of charges at the interface is facilitated and the recombination is hindered, so a higher fill factor is obtained and the efficiency is further improved to 14.28%. Our devices also exhibit good long-term durability and excellent ultraviolet stability. Based on the fully low-temperature preparation process, carbon-based flexible devices are further developed with an optimal efficiency over 9% and considerable mechanical stability, which can serve as the roof-top photovoltaics and power sources for wearable devices. Image 1 • Fully low-temperature processed and flexible carbon-based PSCs with excellent efficiency and stability are demonstrated. • First use of CdS as electron transport layer for carbon-based PSCs. • With the decoration of PCBM, efficiency of the best-performing device is greatly enhanced. [ABSTRACT FROM AUTHOR]

Abstract Organic-inorganic lead halide perovskite solar cells have garnered enormous interest in scientific communities due to comparable power conversion efficiencies and solution-processed fabrication techniques. Among them, carbon-based perovskite solar cells seem to be one of the most promising candidates for addressing the stability issue while suffering from inferior efficiency or high processing temperature. Herein, we introduce low-temperature processed Zn-doped SnO 2 (below 200 °C) as an effective electron transport layer in perovskite solar cells for the first time, and demonstrate a low-temperature carbon-based device with Cu-phthalocyanine as hole transport layer. We find that Zn doping contributes to a more suitable energy level alignment and an improved conductivity for SnO 2 films. As a result, the electron transfer and extraction are enhanced and the charge recombination is suppressed. In addition, devices with Zn-doped SnO 2 have a wider depletion region, leading to an enhanced photovoltaic performance. An optimal efficiency of 17.78% can be obtained after 2 mM Zn doping. Furthermore, these devices, introducing highly stable and hydrophobic Cu-phthalocyanine and carbon, maintain almost 100% of their initial efficiencies over 1200 h in ambient air. Our study paves the way for developing highly efficient and flexible carbon-based perovskite solar cells. Graphical abstract 17.78% efficient low-temperature carbon-based planar perovskite solar cell using Zn-doped SnO 2 electron transport layer is demonstrated. Zn doping contributes to a more favorable energy level alignment, an improved conductivity and a wider depletion region, resulting in an enhanced performance. The low-temperature and solution process realize flexible perovskite solar cells. Unlabelled Image Highlights • A high efficiency of 17.78% is achieved among carbon-based perovskite solar cells. • The whole process is conducted at low temperature (below 200 °C), enabling the fabrication of flexible devices. • The low-temperature processed Zn doped SnO 2 is introduced as an electron transporting layer in perovskite solar cells. • Excellent stability is obtained by utilizing CuPc and Carbon as hole transporting layer and electrode. [ABSTRACT FROM AUTHOR]

Abstract Fullerenes have been widely used as the electron transport layers (ETL) for planar-heterojunction perovskite solar cells (PSCs), due to their superior abilities in electron transporting, hysteresis suppression and low-temperature processing. Here, we demonstrate a novel inverted PSC with evaporated C 60 as ETL and dopant-free copper phthalocyanine (CuPc) as hole transport layer (HTL). The C 60 ETL can not only transport photogenerated electrons, but also passivate grain boundaries and surfaces of perovskite films effectively. By optimizing the thickness of the C 60 ETL, a champion power conversion efficiency (PCE) of 16.72% is obtained with almost no hysteresis and less than 10% decay in efficiency is observed during a two-week stability test. To the best of our knowledge, this is the highest efficiency of the inverted PSCs employing CuPc as HTL. For comparison, the devices using PCBM as ETL are also prepared and only achieve a highest efficiency of 15.74%. Various characterizations and analyses attest the enhanced charge transport and extraction as well as suppressed charge recombination and hysteresis for the C 60 -based devices. Since all the processes are accomplished under a low temperature, this enable us to fabricate flexible PSCs on polyethylene terephthalate (PET) substrates with a highest PCE of 12.96%. Our work provides a new strategy for fabricating cost-effective, highly efficient and hysteresis-free flexible PSCs in mass production. Graphical abstract Novel efficient C 60 -based inverted perovskite solar cells with negligible hysteresis are demonstrated. A champion power conversion efficiency (PCE) of 16.72% and 12.96% is obtained for the devices prepared on rigid and flexible substrates, respectively. Image 1 Highlights • Novel inverted perovskite solar cells (PSCs) with Cu-phthalocyanine and C 60 as HTL and ETL, respectively. • 16.72% efficiency is obtained, which is the highest efficiency of the inverted PSCs employing CuPc as HTL. • 12.96% efficiency is obtained for the flexible device. • Almost no hysteresis is observed. • Cost-effective, easy to prepare and highly stable. [ABSTRACT FROM AUTHOR]

Electron transport layer (ETL), functioning as the electron transportation and extraction layer as well as hole-blocking layer, plays an important role in planar perovskite solar cells (PSCs). Majority of the state-of-the-art PSCs contain a TiO 2 ETL always requiring a high temperature (500 °C) treatment, which is both energy-consuming and incompatible with flexible substrates, thus hindering large-scale application in flexible devices. Here, we demonstrated a low-temperature (70 °C) solution-processed Mg-doped rutile TiO 2 as ETL in planar PSCs, while the thermal-evaporated copper phthalocyanine (CuPc) and doctor-bladed carbon were introduced as the hole transport layer (HTL) and counter electrode, respectively. The as-prepared PSC obtains a 15.73% power conversion efficiency (PCE), which is quite an excellent efficiency among carbon-based planar PSCs, getting an increase by 16% compared to the 13.56% PCE of the pristine TiO 2 -based device. The prominent increment is mainly attributed to the faster charge extraction, better electrical conductivity and suppressed charge recombination of Mg-doped TiO 2 . Besides, using highly stable CuPc and commercial carbon makes the as-prepared PSCs highly durable over 30 days when exposed to the ambient air with a relative humidity of 50%. Since all the processes are conducted under 100 °C, our work paves a way for developing cost-effective and highly stable PSCs compatible with flexible substrates. [ABSTRACT FROM AUTHOR]

Solution-processed titanium (IV) oxide bis(2,4-pentanedionate) (TOPD) as an electron extraction layer (EEL) and the blend of thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM) as a photoactive layer with a power conversion efficiency ( PCE ) of 9.15% are demonstrated. Analysis of the current-voltage ( J-V ) characteristics under dark conditions provides information on the weaker leakage current of TOPD-based polymer solar cells (PSCs) compared to ZnO-based PSCs. By investigating the photovoltaic performance under different light illumination intensities, we achieved an improvement of photovoltaic performance under weak light illumination intensity for TOPD-based PSCs. The enhanced photovoltaic performance under weak light illumination intensity for TOPD-based PSCs can be experimentally explained by the higher open-circuit voltage ( V OC ) value under lower light illumination intensity compared to ZnO-based PSCs. This indicates that the TOPD layer in the PSCs reduced the probability of charge carrier recombination at trap sites and improved the charge carrier collection and transport efficiency under weaker light illumination intensity. Simultaneously, the similar fill factor and short circuit current density of two PSCs can be experimentally explained by the weak bimolecular recombination between the photoactive layer and indium-tin-oxide electrode with the different EEL materials under different light illumination intensity. [ABSTRACT FROM AUTHOR]

Ternary blend films, obtained by introducing a third component (a second acceptor as the third component) to a binary polymer solar cell (PSC), are a promising ternary strategy because the light absorption range, surface morphology, and charge carrier transport of the photoactive layer may be optimized, as can the energy level alignment between the donor and the acceptor. In this work, acceptors such as the short-wavelength-absorption polymer N2200 and the long-wavelength-absorption small molecule FOIC were combined with the donor PBDB-T-2F to construct ternary blends. The optimized ternary PSC could achieve a power conversion efficiency (PCE) of 13.98%, which is higher than the efficiencies of binary PSCs based on PBDB-T-2F:FOIC (12.65%) and PBDB-T-2F:N2200 (9.36%). The enhanced PCE of the ternary PSC is based on the high electron mobility, balanced charge transport, optimized surface morphology and charge carrier kinetics and the extended light absorption of the ternary photoactive layer, realized by adjusting the ratio of FOIC:N2200. Our results indicate that mixing a polymer acceptor into a binary photoactive layer to form a ternary blend photoactive layer is a valuable strategy for improving photovoltaic performance. Image 1 • Ternary PSCs were fabricated with F–N2200 as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved photon harvesting at the donor–blend acceptor interface. [ABSTRACT FROM AUTHOR]

Planar-structure perovskite solar cells have attracted more and more attention, because their simple and low-temperature preparation processing. However, the performance of perovskite solar cells is currently limited by defect-induced recombination at interfaces between perovskite and charge transport layers. In this work, a filmy poly methyl methacrylate (PMMA) layer introduced in Perovskite/Spiro-OMeTAD interface to passivate the interfacial and interganular defects, by which a high open-circuit voltage (1.18 V) is acquired, and the optimal device shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. Femtosecond transient absorption measurement confirms a significant reduction in non-radiative recombination for passivated devices. Mott-Schottky measurement indicates improved flat band potential and carrier density in passivated devices, consisting with the increased voltage. In addition, PMMA film can protect perovskite film from moisture and oxygen erosion. The unsealed device still maintains 95% of the initial efficiency under ambient conditions with 60% relative humidity for one month. This approach solves one of the main limitations of interfacial recombination and shows its potential to improve the performance of perovskite solar cells in the future. • An ultrathin polymer film is used to passivate the interfacial and intergranular defects in PSCs. • The modified PSC shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. • The fs-TA measurement is implemented for analyzing transfer and recombination dynamics of the photo-generated carrier. • The PMMA film plays the role of encapsulation which could protect perovskite film from moisture and oxygen erosion. [ABSTRACT FROM AUTHOR]

Fullerene‐free organic solar cells (OSCs) are fabricated using a blend of J61 polymer as donor and the blend of m‐3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexyl phenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′] dithiophene (ITIC) and ITIC‐Th as electron acceptor. The blend of m‐ITIC and ITIC‐Th as electron acceptor due to the similar lowest unoccupied molecular orbital energy levels and good compatibility among J61, m‐ITIC, and ITIC‐Th, are beneficial for the small energy barrier at the m‐ITIC:ITIC‐Th interface. Simultaneously, the ternary photoactive layer can maintain the optimize film morphology and beneficial to ensure effective suppression of charge recombination at the three kind materials interface. The power conversion efficiency of ternary OSCs achieves to 12.57% when the blend of m‐ITIC:ITIC‐Th (the ratio of m‐ITIC:ITIC‐Th is 40:60) as electron acceptor, with enhanced open‐circuit voltage (VOC) of 0.91 V, short‐circuit current densities (JSC) of 19.94 mA cm−2, and fill factor of 69.6%. Moreover, the optimal ternary OSCs show enhanced thermal stability and photostability than the binary OSCs. This study indicates that the blend of m‐ITIC and ITIC‐Th as electron acceptor and J61 as donor is a promising strategy to fabricate high performance and stable OSCs. [ABSTRACT FROM AUTHOR]

SnO 2 electron transport layers (ETLs) had an essential role in the n-i-p structure of perovskite solar cells. Improving the quality of the electron transport layer and enhancing interfacial contacts were key factors in the fabrication of high-performance perovskite solar cells. Therefore, a non-ionic polymeric polyacrylamide (PAM) modified SnO 2 colloidal solution with improved clustering of SnO 2 nanoparticles was presented to form a uniform and dense SnO 2 electron transport layer. The results demonstrated that no pinhole pores were found at the interface where the PAM-modified electron transport layer and the light absorbing layer came into contact, a structure that facilitated carrier transport and reduced carrier recombination at the interface location. Further beneficial effects were revealed by femtosecond Fs-TA measurements and trap of states (tDOS) analysis, where the carrier lifetime τ 2 decreased from 306.7 ps to 137.8 ps and the trap density of states of the film also decreased significantly. Correspondingly, the SnO 2 -PAM device exhibited an optimum efficiency of 21.61 %. Fantastic device stability was obtained due to the interaction of excellent contact at the SnO 2 /FAPbI 3 interface, and 85 % of the initial efficiency was maintained when placed in air for 1000 h for photo-aging tests, thereby improving the stability of FAPbI 3 grains. This method of improving the quality of tin oxide colloidal solutions provided a novel and simple way to prepare efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]

CsPbIBr 2 perovskite, as a promising light harvester, possesses the most balanced bandgap and stability characters among all-inorganic perovskite materials. However, the poor quality of the traditionally one-step solution-processed CsPbIBr 2 film always leads to a severe recombination loss and thus a low output potential difference (V oc). Herein, we demonstrate a novel vapor-assisted deposition strategy to construct high-quality CsPbIBr 2 films for the first time, in which the crystallization kinetics of the CsPbIBr 2 is more easily controllable than that of the one-step spin-coated one. The PbBr 2 film acting as the template in the CsPbIBr 2 crystal growth is firstly prepared via an antisolvent-washing technique and CsI is then vacuum evaporated onto the PbBr 2 layer. By precisely tuning the thickness of the CsI film, highly phase-pure and crystallized CsPbIBr 2 crystals are successfully obtained. The optimized CsPbIBr 2 film also exhibits a homogeneous morphology and full coverage over the substrate with large grain sizes up to microscale and ultrahigh light absorption capability. The corresponding carbon-based CsPbIBr 2 solar cells achieve a champion power conversion efficiency of 8.76% with a superior V oc of 1.289 V. The large-area (1 cm2) devices also deliver an efficiency of 6.78% with an impressive V oc of 1.336 V. Moreover, under the protection of the highly hydrophobic and chemically stable CuPc layer and carbon counter electrode, the unencapsulated devices present excellent moisture and thermal stabilities. Our work provides a new approach for the preparation of cost-effective, highly efficient and robust CsPbIBr 2 photovoltaics. Vapor-assisted deposition of CsPbIBr 2 films for highly efficient and stable carbon-based planar perovskite solar cells with superior V oc are demonstrated. A champion PCE of 8.76% with an superior V oc of 1.289 V as well as excellent moisture and thermal stabilities are achieved. Image 1 • A novel and facile vapor-assisted deposition method is developed to fabricate CsPbIBr 2 perovskites for the first time. • Highly phase-purity and crystallized CsPbIBr 2 films with large grain sizes are obtained. • A high PCE of 8.76% with a superior V oc of 1.289 V is achieved. • A PCE of 6.78% with an impressive V oc of 1.336 V is gained for the large-area (1 cm2) devices. • Excellent moisture and thermal stabilities are obtained for our devices. [ABSTRACT FROM AUTHOR]